The aim of this study was to examine in vitro the mechanical interlocking of an experimental implant made of E-glass fibre-reinforced polymethyl methacrylate (PMMA)-based composite (FRC) to dental stone. FRC implants with a porous surface were embedded into the dental stone, which was chosen to simulate bone ingrowth into the porous surface of the implant, after which push-out tests were performed. PMMA cylinders with smooth and grooved surface were used as controls. In addition, the release of residual methyl methacrylate monomer (MMA) into water from FRC and control implants with different compositions and fabrication methods was determined using high performance liquid chromatography (HPLC). The highest push-out force (2149 +/- 263 N) was measured for the implants with grooved surface and the lowest value for the implants with smooth surface (194 +/- 68 N). The push-out forces were over five times higher for FRC implants with a porous surface (958 +/- 217 N) than for implants with smooth surface. During the first day of testing, the MMA release into water was 1.4-2.8 times higher from the FRC implants than from the control PMMA implants, depending on fabrication method. With time, the difference between the implants diminished. (c) 2006 Springer Science + Business Media, Inc.